SAT618 Uncovering The Role Of O-glcnacylation In Pituitary Adenoma Pathogenesis: Insights From Corticotroph Tumors

Disclosure: L.J. Massman: None. R. Gonzalez: None. B. Laing: None. D. Coss: None. A.G. Ioachimescu: None. N. Zwagerman: None. S. Olivier-Van Stichelen: None. Functioning corticotroph pituitary adenomas are associated with high mortality, morbidity, and a high propensity of biochemical recurrence postoperatively. Silent corticotroph adenomas cause mass-effect manifestations and have an increased risk for tumor regrowth. The pathogenetic mechanisms responsible for the clinical course of corticotroph PA are poorly understood. In this study, we investigated the role of the O-GlcNAc posttranslational modification in their pathophysiology. O-GlcNAcylation is involved in protein signaling pathways and deregulated in cancers and diabetes. First, we performed RNA-sequencing in functioning and silent corticotroph and gonadotroph adenomas (n=25). We discovered that O-GlcNAc enzymes were upregulated in ACTH-secreting corticotroph tumors and correlated with larger, more invasive tumors. Also, an in vitro mechanistic analysis of corticotroph tumor cells (ATt-20) demonstrated that O-GlcNAcylation was essential for their proliferation and secretory ability. Specifically, O-GlcNAcylation affected Proopiomelanocortin mRNA splicing and stability, suggesting a new mechanism of fast hormonal response in corticotropes. Overall, our study indicates a key role for O-GlcNAcylation in corticotroph adenomas’ cellular proliferation and hypersecretion. Presentation: Saturday, June 17, 2023